Pachybrachis gibsoni Barney, 2018

Barney, Robert J., 2018, Definition and Revision of the Atomarius Species-Group of North American Pachybrachis Chevrolat (Coleoptera: Chrysomelidae: Cryptocephalinae), Including Descriptions of Nine New Species, The Coleopterists Bulletin 72 (1), pp. 9-74 : 43-46

20. Pachybrachis gibsoni Barney , new species Zoobank.org/ urn:lsid:zoobank.org:act:92AF041E-658A-40C9-B1E2-6A2AC8FA6057 ( Fig. 20 , Map 3B)

Holotype. Male, labeled “ WISCONSIN: Sauk

Co. / Spring Green Pres SNA / 43.1791 o N

90.0606 o W / 10.vi.2016 R. Barney [printed, white paper] // [circular blue disc signifying dissection by RJB] // HOLOTYPE / Pachybrachis / gibsoni / R. J. Barney 2017 [printed, black on red paper].” Deposited in MCZ. The specimen is point-mounted with genitalia affixed to a second point. It is in excellent condition with all appendages intact. There are 19 paratypes (966 10♀♀) with identical collecting data.

Paratypes. 31366 275♀♀. See Appendix 20.

Description. Male. Yellow with fuscous punctures, standard maculae diffuse, often appearing almost completely black and heavily punctured; L = 1.73–2.03 mm (mean = 1.90 mm, n = 10); W = 0.94–1.15 mm (mean = 1.04 mm, n = 10); L/ W = 1.78–1.86 (mean = 1.83, n = 10). Head: Slightly wider than thoracic apex, HW = 0.63–0.74 mm (mean = 0.69 mm, n = 10); eyes widely separated, IOD = 0.18–0.24 mm (mean = 0.21 mm, n = 10); IOD/HW = 0.29–0.36 (mean = 0.31, n = 10); face yellow with black, median line extending down from vertex between eyes, forming paired, yellow, inverted triangular maculae, often reduced to appear as entirely black. Pronotum: Yellow, heavily punctured, black, M-shaped macula broadly diffuse, often only leaving small, scattered, yellow spots, punctation to lateral margins, PL = 0.55–0.65 mm (mean = 0.61 mm, n = 10); PW = 0.81–0.99 mm (mean = 0.90 mm, n = 10); PL/PW = 0.65–0.71 (mean = 0.67, n = 10). Elytra: Confused punctures in baso-sutural region, striae irregular, marginal interspace mostly punctate, often appearing entirely black with yellow after declivity. Pygidium: Black,sometimes with 2 small, oval, yellow maculae. Venter: Black. Legs: Black with standard yellow spots. Genitalia: Median lobe in en-face view with large, oval OS with shaft widest near midpoint, PRL reduced, with large, sclerotized basal plates. POL, best seen in lateral view, deflexed at near 65° ALA, thereby creating a triangular, arrowhead-shaped area with a gently rounded terminus and 2 barely perceptible, posteriorly projecting denticles. Setae present along edges of deflexation ( Fig. 20 ). One hundred and four males from 24 states were dissected.

Female. As in male, except L = 2.06–2.25 mm (mean = 2.14 mm, n = 9); W = 1.11–1.26 mm (mean = 1.18 mm, n = 9); L/W = 1.75–1.86 (mean = 1.85, n = 9); HW = 0.74–0.82 mm (mean = 0.78 mm, n = 9); IOD = 0.23–0.30 mm (mean = 0.27 mm, n = 9).

Etymology. This species is named in recognition of Gibson Ray Barney, Blacksburg, Virginia, who serves as an inspiration.

Remarks. Several specimens of P. gibsoni from Massachusetts were originally identified by Fall as a possible variation of P. relictus . Externally, this species is often very difficult to separate from darker versions of P. atomarius , P. stygicus , P. nigricornis , and P. dixianus . The dissected median lobe must be rotated at just the correct angle to notice the small denticles at the ALA.

Distribution. This species is distributed across the eastern USA and west to the 100 th meridian (Map 3B).

Biological Notes. Label data reported collection on A. canescens in Illinois, Ceanothus sp. (Rhamnaceae) in Massachusetts, Quercus sp. in North Carolina, and Quercus velutina Lam. in Michigan.

Specimens Examined. See Appendix 20.

Figures

Fig. 20. Pachybrachis gibsoni, holotype. A) Dorsal habitus, B) Lateral habitus, C) Face, D) Pygidium, E) Median lobe of aedeagus, lateral view, F) Median lobe of aedeagus, en-face view.